DESCRIPTION (Applicant's Description): Dr. Ebbinghaus is a senior fellow who has devoted more than 60% of his last five years to basic research while completing clinical training in Internal Medicine, Medical Oncology, and Hematology at UAB. In addition to completing a formal core graduate program in Cell and Molecular Biology, Dr. Ebbinghaus joined an ongoing laboratory effort in Dr. Donald Miller's laboratory and initiated a program of designing triplex-based anti-gene strategies to specifically inhibit the HER-2/neu oncogene. Dr. Ebbinghaus will join the faculty of the Division of Hematology-Oncology at the completion of his fellowship and devote over 80% of his time to his laboratory efforts. Dr. Ebbinghaus will be given laboratory space in close physical proximity to Dr. Miller's laboratory in the Wallace Tumor Institute so that he may continue to use the critical equipment in Dr. Miller's laboratory and the Animal Core Facility in this building. The NCI Clinical Investigator Award will support Dr. Ebbinghaus in his transition from a senior fellow to an independent investigator in his own laboratory. The HER-2/neu oncogene plays an important role in many types of human cancer. There is good data to support the concept that inhibiting HER-2/neu expression will reverse the malignant phenotype and have beneficial clinical effects in patients with HER-2/neu related malignancies. Oligonucleotides are particularly attractive as specific inhibitors of oncogene expression since they have the ability to bind to target DNA or RNA sequences with very high specificity. Dr. Ebbinghaus and Dr. Miller have investigated the ability of DNA oligonucleotides to bind to the HER-2/neu oncogene promoter and found that these oligonucleotides potently and specifically inhibit HER-2/neu transcription through DNA triplex formation in vitro. The broad goals of this proposal are to determine the ability of triplex formation to inhibit HER-2/neu expression in cell culture and animals by both synthetic DNA oligonucleotides and RNA oligonucleotides transcribed in vivo. This proposal will build on Dr. Ebbinghaus and Dr. Miller's previous experience with triplex forming oligonucleotides in vitro and current work using gene therapy vectors to deliver these oligonucleotides to tumor cells in culture. The specific aims of this proposal are: 1) to characterize the ability of synthetic DNA oligonucleotides to inhibit HER-2/neu expression and alter the malignant phenotype of HER-2/neu expressing tumor cell lines in culture; 2) to characterize the ability of intracellularly transcribed RNA oligonucleotides to form triplex structures in the HER-2/neu promoter and inhibit gene expression in tumor cells in culture; 3) to generate a recombinant adenovirus capable of expressing RNA oligonucleotides designed form triplex structures in the HER-2/neu promoter and characterize its ability to inhibit HER-2/neu expression in tumor cells; 4) to develop an animal model to test the efficacy of synthetic DNA, transcribed RNA, and recombinant adenovirus expressed oligonucleotides to inhibit HER-2/neu gene expression in vivo. The successful completion of these specific aims will generate invaluable insights into the role of HER-2/neu in the cause of certain cancers as well as provide the background for triplex based gene therapies for HER-2/neu related cancer.